Tripod jack



H. E. PAGE TRIPOD JACK sept-17, 1946.

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Sept. 17, 1946. H. E. PAGE -2,407,796

TRIPOD JACK Filed Aug. 17, 1943 2 Sheets-Sheet 2 Patented Sept. 17, f1946 UNITED STATES PATENT OFFICE TRIPOD JACK Herbert E. Page, Pasadena, Calif. Y

Application August 17, 1943, Serial No. 498,930

13 Claims.

This invention has to do with jacks and, more particularly, it relates to hydraulically actuated tripod jacks such as are used for raising loads to substantial heights. Although such jacks have many uses, oney of the chief uses is as an airplane jack.

While tripod jacks are known in the art, heretofore they have had certain inherent shortcomings such as lack of proper rigidity, limitations of height,` dangerous side sway characteristics, slowness of operation, and lack of adequate safety features.

It is one of the objects of my'invention to provide a hydraulically actuated tripod jack in which the tripods are telescopic and are automatically extended in consonance with elevation Yof the load, each of the tripods being comprised of a piston member and a cylinder member.

Another object is to provide a jack capable of effecting quick contact with the load to be lifted by a minimum of effort, this feature being by way of an improvement upon and a novel adap tation of the invention shown in my prior Patent No; 2,154,956.

Another object is to provide a jack utilizing a plurality of liftingV pistons which function to decrease the pumping effort required to lift a given load and which provides desirable safety features against accidental lowering of the load.

Another object of my invention is to provide a hydraulic jack in which hydraulic locks are provided in the tripods to prevent side sway.

Another feature of my invention resides in its double acting pressure generating piston.

In the accompanying drawings I show and in the following description I describe a presently preferred adaptation of the Ainvention from which it will be obvious to those skilled in the art that my invention possesses still further important advantages and may be carried out in other specie physical forms, all within the broader scope of the invention as` dened by the appended claims.

In the drawings:

Fig. 1 is a vertical medial section taken on line I-l of Fig. 2;

Fig. 2 is a top plan View;

Fig. 3 is an enlarged fragmentary sectional view Showing one ofthe valve elements; and

Fig. 4 is an 4enlarged fragmentary sectional View showing another of the valve elements.

The numeral 5 designates a base presenting a cylinder bore l, fluid passageways 8, 9, 9a, l0 and H, a uid reservoir l2, uid chambers i4 and I-5-, a threaded socket I1 and a bifurcated boss I8 which latter provides a fulcrum for the pumping lever 2li. A tubular guide member 25 has its lower end threaded into the socket I'l and presents a cylinder 26. Threaded filling plug 21 is provided for reservoir I2.

A body 3D presents a cylinder bore 32 and a relatively larger cylinder bore 33. Within the top end of bore 33 there is a threaded sleeve 35 within which is slidably mounted a piston 3l. A` stop ring 38 is threaded onto the top end of piston 3l for engagement with the top end of sleeve 35 to prevent further inward movement of piston 31. The inner end of the piston 31 is reciprocably mounted in cylinder 26, which cylinder communicates with bore 33, an extension screw 39 being threaded into an internally threaded longitudinal bore 31a in piston 31. rIhe tubular member sli'dably ts in bore 33 of the body, a guide ring 40 being threadedly mounted in the bore. A stop ring 4l is threaded onto the` top end of tube 25 and is adapted to be engaged by the top end of ring lill when the body reaches the upper limit of its movement relative to the tube, as will be hereinafter described. Ring 4| has a plurality of fluid-passing ports denoted by the dotted lines Ma in Fig. 1.

A piston 45 reciprocates at one end in cylinder 32 and at the other end in cylinder 1. The upper end of cylinder 32 communicates with the bore 5l of a valve housing 59 through port 52. The lower or inlet end of the bore 5| communicates with a fluid reservoir 55 in the body by means of tube 56 carrying a screen 5l at its lower end. Another port 58 in the body provides communication between valve housing bore 5l and cylinder 33.

A poppet 5B, having oppositely disposed stems 6l, 62, seats by gravity towards the reservoir in b-ore 5I and a ball valve 65 seats towards the reservoir in bore 5l. A coil spring B3, seating against a plug 5d threadedly mounted in bore 5l, bears against and normally retains ball 65 against its seat. This spring is of a strength to maintain ball seated during initial upward movement of the body to establish contact with the load to be lifted, but is yieldable to pressure generated by the pressure stroke of piston when further upward movement of the body is resisted by the load being lifted, thus permitting uid. to flow into cylinder 33 and provide lifting pressure therein.

The valve housing is held in the-:body bore 'l5 by a snap ring 'l5 and packing rings 1l are interposed between the housing and the side wall Qf the bore.

Three bifurcated bosses 88 are provided on the base 5 and between the bifurcations of each of the bosses the lower end of a tube 82 is pivoted by means of pin 83. The interior of each tube 82 provides a piston chamber 85 within which a piston 86 reciprocates. A rod 81 connects each of the pistons 86 to an arm 88 formed integral with the upper end of the body, the upper end of the rod being pivotally connected to the arm by pin 89. Thus the tubes 82, pistons 86 and rods 81 provide tripods for the body. A plug 88 threaded into the top end of each tube l82 provides a bearing for reciprocation of the rod 81.

The lower end of each cylinder chamber 85 communicates with base chamber I5 through a flexible tube 95, the three tubes being connected into the port by means of three connection members 85. Chamber I5 communicates with the cylinder bore 1 through passageway 8, the passage of uid from chamber yI5 to cylinder 1 being prevented by ball check valve 91 seating towards cylinder 1. Chamber I5 also communicates with reservoir I2 through port I8, the latter communication being controlled by valve member 98 threadedly mounted in the base. To enable fluid to be drawn from reservoir l2 into cylinder 1 upon the upstroke of piston 45, passageways 9, 9a are provided in the body in communication with chamber |4, the return movement of uid to the reservoir being prevented by a ball valve 9.9 seating towards the reservoir.

The upper end 85a of the chamber 85 in each tube 82, above the piston 86 therein, communicates With the reservoir I2 through a flexible tube |88, a three-way valve 8| being interposed between the ,tubes |88 and |82. The valve |8| is of conventional construction and a hand wheel |83 is provided for manually opening and closing thevalve so that it may be closed to trap hydraulic fluid in the chambers 85 above the pistons therein, for the purpose to be hereinafter set forth.

Cylinder 33 also communicates with reservoir 55 through a portJ |85 and valve member |86, which latter consists of a valve housing |81 held in a body bore |88 by a snap ring |89. A poppet I I8 is slidably mounted in the bore of thehousing |81, seating towards the reservoir and being urged against its seat by spring A safety valve is incorporated in the poppet and consists of a plug ||5 having a port v| I6 against whose periphery an auxiliary hollow poppet I |1 is urged by a spring IIB, fluid passing through ports ||9 provided through poppet ||1. Housing |81 has a tubular extension |28 disposed in the reservoir, the lower end of the tube |28 being closed and the side wall being perforated as shown at |2|.

Operation of the device is as follows: To initially contact the top end of the screw extension 39 or sleeve 35 with the work tobe lifted, lever 28 is operated to reciprocate piston 45 in cylinders 32 and 1, respectively, the upper end of the piston operating in cylinder 32 and the lower end operating in cylinder 1. Upon each downward stroke of piston 45 niiuid is drawn from reservoir 55 past poppet 88 and through port 52 into the upper end of Acylinder 32, and on each llPWard stroke of the piston in cylinder 32, prior to establishing contact with the Iwork to be lifted, the spring-pressedvalve 65 and poppet 88 trap the fluid in cylinder 32, causing the body to be lifted into contact with the work by virtue of the iluid pressure between the top efnd of piston 45 and the adjacent end of cylinder 32. Valve spring 63 is made strong enough to 11016, Valve 6 5 through passageway |35,

seated until a substantial resistance, such as is offered by contact with the load to be lifted, is encountered. During this initial movement of the body, uid is drawn from reservoir 55 past poppet I8 and through port |85 into cylnder 33, any unsafe back pressure on poppet ||8 being relieved by the auxiliary, oppositely seating poppet ||1. When the load is contacted, its resistance to further movement of the body 38 causes valve 65 to be unseated against its spring by the pressure generated on the upstroke of piston 45 and the liuid is therefore forced into cylinder 33 through port 5B to lift the body relative to the base. During this operation, each upward `stroke of piston 45 in cylinder 1 draws fluid from reservoir I 2 through ports 9, 9a, into cylinder 1, and on each downward stroke of piston 45 in said cylinder lthe fluid thus previously drawn from the reservoir is forced past valve'91 into the lower ends of the respective cylinder chambers to exert lifting pressure against the respective pistons 86. The extension screw 39 may be manually rotated, as by inserting a rotating pin in hole 39a, to unscrew it from the threaded bore 31a. ment of pistons 88 in chambers 85 fluid is drawn from the reservoir I2 through tube |88, there is always some fluid in the upper ends of the chambers 85 and by closing valve I8I this fluid may be trapped in the chambers and, together with the fluid pressure against the bottom of pistons 86, side sway of the jack is prevented.-

The operation of piston 45 in the respective cylinder-s 32, 1 being alternate, when the body is being lifted by pressure in cylinders 32 or 33, uid will be drawn into cylinder 1 from reservoir I2 and when the body is being lifted by operation of piston 45 in cylinder 1, fluid will be drawn into cylinders 32 and 33 from reservoir 55.

It is possible to provide a hydraulic lock in cylinder 85 even before the load is fully elevated, and to facilitate this I provide an auxiliary inlet passageway |35 from passage 8 to reservoir I2, passage of fluid from the reservoir to cylinder 1 through this passageway being prevented by check valve |36 seating towards cylinder 1,. Thus if it be desired to lock pistons 86 against movement during the lifting operation-as may sometimes be necessary when a load exposedto heavyv wind pressure is being lifted and such lock is necessary to prevent side sway-valves |8| and 98 are closed. Thereafter the pressure stroke of piston 45 in cylinder 32 will lift the load by projecting piston 31 from the body 38, as is the case when body 38 reaches the upper limit of its travel, and the pressure stroke of piston 45 in cylinder 1 merely returns fluid to reservoir I2 When piston 45 is being operated in cylinder 1 to raise pistons 88,

the check valve |36 is held closed by the screw` plug |31. Also, if it be desired to raise the load by lifting body 38 or piston 31 alone and without providing a hydraulic lock in cylinders 85, this can be accomplished by unscrewing plug |31 to permit valve |36 to be raised. Y

In lifting extremely heavy loads it may sometimes require too much manual pumping pressure to lift body 30 or piston 31 by pressure generated in cylinder 32, and in such cases it is desirable to utilize only the pressure generated in cylinder 1 to raise the three pistons 86. To accomplish this it is only necessary to screw valve |38 inwardly to open valves 88, 65 which renders cylinder 33 ineffective.

To lower the load, valve IUI is opened and the' Inasmuch as upon each downward movevalve screw 98 `is unscrewed to permit the iiuid trapped below the pistons inthe respective cylinders 8'5 -to flow back into `the reservoir l2 and thus relieve the pressure in those cylinders. Either simultaneously or subsequently, the valveactuating screw 139 is screwed into the valve housing '5D Vuntil its "tapered inner end contacts stem 6l and lifts poppet El! off its seat, which `force relieves the pressure in cylinder 32 and further operation vof the Ascrew L30 causes stem 62, lwhich is normally spaced from ball `|55, to contact and lift said ball off its seat to relieve .the pressure Vin cylinder 33. Either one of the screws 98 or l may be employed to control the rate 'of descent by `control-ling the rate of return flow-of the hydraulic iiuid to the reservoir.

|-Ihe advantages of my ack nwill be readily understood when it is realized that such devices are employed to lift loads to substantial heights, often of the order of eight feet or more, and when the load surface is exposed to the wind a considerable side sway would develop but for my novel construction wherein the tripod pistons 86 may be locked against reciprocation in the tubes 82, Moreover, the multiple cylinders in the pistonsV materially reduce the manual eiort required to lift a given load and also distribute the stresses. The double acting piston 45 also saves `considerable time. The automatic quick contact -feature of my device is also a great advantage as a time and labor saver.

I claim:

l.. In a jack, the combination of a base, a telescopic work-engaging member mounted for telescopic movement perpendicular to the base, pressure-actuating ymeans for extending the work-engaging member, and means for laterally supporting the work-engaging member compris- -i-ng la plurality oi vtelescopic support members, each including a cylinder and a'piston, `disposed symmetrically around and inclining towards the work-engaging member, each -oi said telescopic support members being secured at its opposite ends to thebase and work-engaging member, and hydraulic pressure-generating means vcommunicating with the cylinders of the support members.

2, In a jack, the combination of a base, a body movable relative to the base, a telescopic tripod supporting the body from the base, each leg of the tripod comprising a tubular member providing a piston chamber therein and a piston member reciprocably mounted in `the chamber, one of said 'members being secured Vto the base and the other lmember being secured to the body, hydraulic means cooperating with the chamber of `each leg at opposite sides of the piston therein whereby to provide fluid pressure on opposite sides of the piston, and fluid pressure generating means independent of said hydraulic means cooperating With the body and vbase to raise the body relative to the base.

3. In a jack, the combination of a base, a body movable relative to the base, a telescopic tripod supporting the body from the base, each leg oi the tripod comprising a tubular member providing a piston chamber therein and a piston mem-ber reciprocably mounted in the chamber, one of said members being secured to the base and the other member being secured to the body, a fluid reservoir, a iluid pump communicating with the reservoir and with each piston chamber below the piston therein whereby to generate fluid pressure acting against the piston, a line providing communication between the reservoir 6 Y Aand each piston chamber above the piston therein, valve means operable to open `and close said line, and hydraulic means for moving the body relative :to the base,

4. the combination of a base, 'a body rmovable relative yto the base, cooperating piston and piston chamber means provided in the base and body, a telescopic tripod supporting the body from the basaeach leg of the tripod comprising a tubular member providing a cylinder and a piston member reciprocably mounted therein, vone oi said members being pivotally connected to 'the base and the other being pivotally connected (to the zbody, `said body `and base presenting .respectively 'oppositely opening concentric cylinder bores, ,a pumping piston reciprocably mounted at one in 'one of the cylinder bores and at its other Vend in the other cylinder bore, means providing communication between one of said cylinder bores and said piston chamber and means `providing communication between the ,other Acylinder bore and the cylinder in each of the respective legs, whereby reciprocation of said pumping piston valternately generates pressure in the piston chamber and in the cylinders in the legs, respectively,

5. In a jack, the combination of a base, a body movable relative to the base, cooperating piston and piston chamber means provided by the base and body, a telescopic tripod supporting the body from the base. each leg ofthe tripod comprising a tubular member providing a cylinder .and a piston member reciprocably mounted therein, one of said members being pivotally connected to the base and the other being pivotally connected to the body, said body and base presenting respectively oppositely opening concentric cylinder bores, a pumping piston reciprocably mounted at one end in one of the cylinder bores and at its other end in the other cylinder bore, means providing communication between one of said cylinder bores and said piston chamber and means providing communication between the other cylinder bore and the cylinder in each of the respective legs, whereby reciprocation of said pumping piston alternately generates pressure in the piston chamber and in the `cylinders in the legs, respectively, and means for providing iluid pressure inthe cylinders of the respective tubular members in a manner to oppose movement of the pistons therein by virtue of pressure generl ated by the pumping piston,

'61, In la jack, the combination of a base presenting an upright tubular guide member, a body presenting a cylinder `slidably receiving the guide member, a work-lifting piston slidably mounted in the body and reciprocably disposed Vin the tubular guide member, a cylinder bore in the body substantially parallel to the said cylinder, a rluid reservoir in the body, a fluid passageway in the Abody providing -communication between the reservoir and cylinder bore, a check valve the passageway seating towards the reservoir, a pumping piston reciprocably mounted in the cylinder bore` a second iiuid passageway in the body providing communication between the cylinder bore and the first-mentioned cylinder, a check valve in the second fluid passagewayl seating towards the sai-rl cylinder bore, spring means normally maintaining the last-named ,check valve seated and beingof a strength suiicient to oppose pressure generated bv the pumping p-iston when the work-lifting piston is out of contact with the work to be lifted` but yieldable to said pressure `when the work-lifting piston `is bur- 7 dened with the load to be lifted, and a telescopic tripod pivotally secured at one end to the body and pivetally secured at its other end to the base.

7. In a jack, the combination of a base presenting a fluid reservoir, a first cylinder bore and a second cylinder bore, a body movable relative to the base and presenting a chamber concentric with the rst cylinder bore in the base and a uid reservoir, a work-lifting piston slidably carried by the body and reciprocably disposed in the second cylinder bore in the base, a pumping piston reciprocably mounted at one end in said iirst cylinder bore in the base and at its other end in said chamber in the body, a tripod having legs each consisting of a tubular member providing a piston chamber and pivotally secured to the base and a piston reciprocably mounted therein and secured to the body, intercommunicating passageways in the base providing communication between the reservoir, the .piston chambers in the tripod legs and the first cylinder bore, a check valve in one of Vsaid passageways preventing passage of fluid from the piston chambers in the tripod legs to the rst cylinder bore but permitting passage of fluid from the rst cylinder bore to the said piston chambers, a second check valve in one of the passageways permitting passage of fluid from the reservoir to the rst cylinder bore but preventing passage of iluid from the first cylinderbore to the reservoir, a manually operable valve controlling passageof fluid from said piston chambers to the reservoir, a uid passageway in the Ybody providing communication between the body reservoir and the body chamber, a check valve in said last-named pas-` sageway seating towards the body reservoir, a second iluid passageway in the body providing communication between the body chamber and the second cylinder bore in the base, a check valve in the last-named passageway seating towards the body chamber, a spring urging the .last-named check valve seated, said spring being yieldable to pressure generated by the pump.. ing piston only when the `work-lifting piston is burdened by a load being lifted, and manually actuated means for unseating the last-named two check valves.

l 8. In a jack, the combination of a base, a work-lifting element movable towards and away from the base, a longitudinally extensible tripod secured at one end to the base and at its other end to the work-lifting element, said work-lifting element presenting a pair of substantially parallel cylinders, a pumping piston reciprocably mounted in the first of the cylinders, a workengaging piston protractable from and reciprocably mounted in the second cylinder, a uid reservoir, fluid passageways establishing communication between the reservoir and the first Cylinder and between the first and second cylinders, and valve means in the passageway between the rst and second cylinders maintaining saidpassageway closed when movement of the worklifting element is not opposed by work beingV lifted, said pumping piston being operable when moved in one direction, in conjunction with the last-named valve means and fluid from the reservoir, to extend the tripod and move the worklifting element into engagement with the work independently of pressure in the second cylinder, and hydraulic means for locking the tripod in such extended position.

9. In a jack, the combination of a base, a work-lifting element movable towards and away from the base, a longitudinally extensibley tripod 8 secured at one end to the base and at its other end to the work-lifting element, said work-lifting element presenting a pair of parallel cylinders, a pumping piston reciprocably mounted in the rst of the cylinders, a work-engaging piston protractable from and reciprocably mounted in the second cylinder, a uid reservoir, fluid passageways establishing communication between the reservoir and the rst cylinder and between n the iirst and second cylinders, and valve means in the passageway between the first and second cylinders maintaining said passageway closed when movement of the work-lifting element is not opposed by work being lifted, said pumping piston being operable' when moved in one direction, in conjunction with the last-named valve means and fluid from the reservoir, to extend the tripod and move the work-lifting` element into engagement with the work independently -of pressure inthe second cylinder, and hydraulic means operable to exert extending pressure on the tripod in response to movement of the pumping piston in the other direction.

l0. In a jack, theV combination of a base, a body, an extensible tripod supporting the body from the base, each leg of the tripod comprising a tubular member providing a piston chamber therein and a piston member reciprocably mounted in the chamber, one of said members being secured to the base and the other being secured to the body, a piston member carried by and projectible from the body, fluid pressure generating means for moving the piston members, and valve means for selectively communicating the fluid pressure to the .said tripod piston members or to the said bodyy pistonmember.

1l. In a jack, the combinationV of a base, a body, an extensible tripod supporting the body from the base, each leg of the tripod comprising a tubular member providing a piston chamber therein and a piston member reciprocably mounted in the chamber, one of said members being secured to the base and the other being secured to the body, a piston member carried by and projectible from the body, hydraulic means so operatively associated with the body andthe piston member carried thereby as initially to move the body relative to the base until the body contacts a load to be lifted and subsequently to move said piston member relative to the body to lift the load, and hydraulic means operable to extend the tripod.

12. In a jack, the combination of a base, a body, an extensible tripod supporting the body from the base, each leg of the tripod comprising a tubular member providing a piston chamber therein and a piston member reciprocably mounted in the chamber, one of said'members being secured to the base and the other being secured to the body, a'piston member carried by and projectible from the body, hydraulic means so operatively associated with the body and the piston member'carried thereby as initially to move the body relative to the base until the body contacts a load to be lifted and subsequently to move said piston relative to the body to lift the load, and hydraulic means operatively associated with the tripod, said last-named means being operable to lock the tripod pistons against movement relative to the tripod piston chambers whereby to prevent side sway of the body.

13. In a jack, the combination of a base, a telescopic work-engaging member mounted for telescopic movement perpendicular to the base, pressure-actuating means for extending the ends to the base and Work-engaginrmember, and hydraulic means cooperating with the respective cylinders of the support members to provide fluid pressure on opposite sides of the 5 pistons therein.

HERBERT E. PAGE. 

